This proposal outlined experimental plans for the following four areas of regulatory mechanisms of acetyl CoA carboxylase. 1) Covalent Modification of Acetyl CoA Carboxylase (ACC): The questions we hope to answer are: 1) What are the properties of ACC kinase and phosphatase and how are these enzymes regulated by the lipogenic hormones?; 2) what are the relationships between mechanisms of covalent modification and allosteric control in the regulation of ACC and lipogenesis?; 3) does covalent modification affect ACC degradation and thus the long-term regulation of ACC? In addition, experimental plans to determine the primary sequence of peptide around the phosphorylation site which controls the activity are described. 2) Regulation of Covalent Phosphorylation by Cellular Energy Status: to substantiate our hypothesis that covalent phosphorylation of ACC is regulated by the conformation of ACC which is affected by energy charge, the regulatory site(s) on ACC which recognize cellular energy signal will be characterized. Also, experimental plans to modify the regulatory sites by photoaffinity labelling are included to ascertain that such modification affects the rate of covalent phosphorylation. 3) Mechanism of CoA Activation of ACC and its Physiological Significance: Our preliminary results suggest that CoA is the physiologically important allosteric positive effector for ACC. We propose here to extend our studies on the mechanism of CoA activation of ACC, the relationship between this new control mechanism and the covalent modification mechanism, and physiological significance of CoA activation of ACC. 4) Adrenergic Receptor Control of Insulin Receptor Function in the Control of ACC: This portion of the proposal outlines some exploratory experiments which attempt to examine whether there is any communication link between two receptors which mediate biologically opposing effects using the ACC system, insulin and the beta-adrenergic receptors, in the isolated rat hepatocyte system.